Changes in the expression of α 2-adrenergic receptor subtypes during maturation of neuronal cells from fetal pig superior cervical ganglia

Abstract

The expression of presynaptic α 2-adrenergic receptor (α 2-AR) subtypes was investigated in cultured neurons from fetal pig superior cervical ganglion (SCG). Cells were incubated with chicken antibodies against α 2A-, α 2B- or α 2C-AR subtypes either alone or together with antibodies against dopamine-β-hydroxylase (DβH, a marker for adrenergic neurons) or against choline acetyl transferase (ChAT, a marker for cholinergic neurons). We found immunoreactivity for all three α 2-AR subtypes in SCG-cells when cultured for 8–11 days. The relative expression of the α 2A-subtype was approximately 1/3 of that of α 2B- and α 2C-AR. Co-localisation of all three α 2-AR subtypes was observed in cells expressing DβH or ChAT. Increasing the potassium concentration in the culture medium increased the expression of DβH and decreased the expression of the α 2A- and α 2C-subtype without altering the expression of the α 2B-subtype. Co-culture of neurons with pig splenocytes enhanced the expression of ChAT and decreased the expression of the α 2B-subtype without altering the expression of α 2A- and α 2C-subtypes. Our results indicate that the three α 2-receptor subtypes are expressed on both noradrenergic and cholinergic nerves. Induction of the noradrenergic phenotype favours the expression of the α 2B-subtype over that of the α 2A- and α 2C-subtype. Conversely, enhancement of the cholinergic phenotype favours the expression of the α 2A- and α 2C-subtypes over that of the α 2B-subtype. Our results suggest that the α 2B-receptor is preferentially associated with noradrenergic nerve endings.